The present invention relates to a repairing material of a brick and a method of repairing a brick, and more particularly a brick used in a device for controlling a flow rate of high temperature liquid materials such as molten steels.
A method of repairing a brick of this type has been known, for example, in Japanese Patent Publication No. (KOKOKU) 60-47230. In this method, the brick is detached and, after cooling the brick, repairing material is coated to a damaged portion and then dried, in which the repairing material comprises a mixture of 50 to 60 wt % of alumina, 20 to 30 wt % of sodium silicate and 20 to 30 wt % of graphite lubricant.
In this method, since the repairing material is merely coated to the damaged portion and dried, the bondability is poor and the repairing material is easily peeled off upon re-use under severe working conditions such as the sliding force of the brick, thus this method can provide no sufficient effect. In addition, this method can be applied only to those cases where the damage is slight. The repair is difficult or almost impossible for those bricks having severe, damage, for example, damage formed to the sliding surface portion in the form of a recess of about 4 to 5 mm. Accordingly, the regenerating ratio is 20 to 30% at the most.
Use of sodium silicate or graphite as the repairing material is preferred, but, since the addition amount of the repairing material is as much as 20-30 wt %, the corrosion resistance at the repaired portion is poor and the mechanical strength is also low. Accordingly, although the brick can be regenerated, the result of use is not satisfactory.
As a result of the present inventors' studies in order to solve the above-mentioned problems, it has been found that by filling a mixture of (1) 70 to 80 wt % of alumina having a grain size of not more than 1 mm, wherein the alumina is composed of 25 to 30 wt % of the above amount with a grain size not passing through a 325 mesh and 45 to 50 wt % of the above amount with a grain size passing through a 325 mesh, (2) 1 to 7 wt % of carbonaceous material having a grain size passing through a 60 mesh, (3) 1 to 5 wt % of magnesia having a grain size passing through a 325 mesh and (4) 10 to 25 wt % of aluminum phosphate, into a damaged part of the brick while maintaining a temperature of the brick of less than about 100.degree. C., and hardening the filled mixture, the repair can be made easily, the damage to considerable extent can be repaired with the regenerating ratio of about 100%, the repairing material can provide sufficient corrosion resistance and high strength, and a working life of the brick can be extended. The present invention has been attained based on the findings.